Graphene quantum dots: Synthesis, applications, and future directions in bioimaging and cancer therapy

Graphene Quantum Dots (GQD) has been extensively used because of its unique electronic, chemical, and photoluminescent properties, which are derived from graphene. They are classified as zero-dimensional nanomaterials. This review article discusses the synthesis strategies of GQDs, which can be broadly categorized into top-down and bottom-up methods including Electrochemical oxidation, Hydrothermal, Chemical oxidation, and Ultrasound-assisted as top-down method and Microwave, Carbonization, Electron beam irradiation, Stepwise organic synthesis as bottom-down method. Every method offers various advantages, such as convenience, scalability, and flexibility to adjust the size and surface features of the quantum dots, altering their bioactivity and functionalization potential. These features make GQDs a suitable platform for various biomedical applications, including bioimaging and cancer therapy. In bioimaging, Graphene quantum dots excel in bio-imaging due to their biocompatibility, photostability, and tunable luminescence, offering deep tissue penetration and applications in fluorescence imaging, MRI, cancer detection, and non-invasive diagnostics. In cancer therapy, GQDs utilize their photothermal and photodynamic properties to induce cancer cell death. This localized treatment enhances effectiveness of the therapeutic without causing damage to surrounding healthy tissues. The review also addresses challenges in the practical application of GQDs, functionalization, while highlighting recent advances and future directions for research. • GQDs synthesized using top-down and bottom-up approaches. • Doping and functionalization improve PL, yield, and applications. • GQDs enable theranostics, drug delivery, and bioimaging. • GQDs show promise in drug, energy, and environmental uses.